1. Field of the Invention
The present invention relates to an inter-LAN connection equipment for packet forward among LANs (local area network) and, in particular, to an inter-LAN connection equipment as a bridge equipment which can effectively forward or discard a packet after learning of an MAC address (media access control address).
2. Description of the Related Art
Conventionally, an inter-LAN connection equipment (or a bridge equipment) for internal learning of a MAC address receives all packets sent from LANs and discards, out of all the packets, a packet whose destination is directed to a node on the same LAN, that is, discards it without being forwarded. The reason for this is that it is not necessary to forward the packet if it is sent to a given node on the same LAN. If being forwarded, the packet involved causes a lowering in the forward efficiency of a forward-destination LAN. For this reason, the packet, being directed to the given node on the same LAN, has normally been discarded by a microprocessor without being forwarded. In this case, the microprocessor determines whether or not a packet should be discarded in accordance with a control program.
Determining whether the packet supplied from the given LAN should be forwarded or discarded has been done in the program processing by the microprocessor. In the conventional inter-LAN connection equipment, however, communication is often carried out on the same LAN and it takes more time to perform discard processing than an ordinary forward processing. Even if use is made of any high-speed microprocessor, it has been difficult to improve the performance of the inter-LAN connection equipment.
In the conventional inter-LAN connection equipment, a packet sent from the LAN is stored in a buffer memory. Then in the case where the packet is to be forwarded or passed, after it has been fully received from its start portion to its end portion, the transmission of the packet to the forward-side LAN is started. For this reason, more time delay occurs in the transmission of the packet than in the absence of any inter-LAN connection equipment. Therefore, the terminal-to-terminal (LAN-to-LAN) communication performance has been markedly lowered in comparison with the communication performance on the same LAN, thus presenting a problem.
A more high-performance inter-LAN connection equipment has been proposed as shown in KOKAI H-4-237232. In this proposal, control is made so as to prevent reception of any packet not requiring any forward, that is, any packet to be communicated on the same LAN. In this case, control is made on an external hardware.
The description of KOKAI H-4-237232 suggests a practical applicability of the packet discard determination technique to the packet forward determination technique, but there is no suggestion as to achieving a high-speed packet forward. Therefore, there is a demand for achieving a high-speed packet forward unit.